Add support for resuming from deep sleep (#259)

* Add support for resuming from deep sleep
Adapted patch from @ccantill to latest head revision.
* Renamed new init method from "resume" to "allocateBuffer"

Author: ThorstenBr

src/OLEDDisplay.cpp

@@ -57,7 +57,7 @@ OLEDDisplay::~OLEDDisplay() {
   end();
 }
 
-bool OLEDDisplay::init() {
+bool OLEDDisplay::allocateBuffer() {
 
 	logBufferSize = 0;
 	logBufferFilled = 0;
@@ -93,6 +93,15 @@ bool OLEDDisplay::init() {
   }
   #endif
 
+  return true;
+}
+
+bool OLEDDisplay::init() {
+
+  if(!allocateBuffer()) {
+    return false;
+  }
+
   sendInitCommands();
   resetDisplay();
 

src/OLEDDisplay.h

@@ -160,7 +160,12 @@ class OLEDDisplay : public Stream {
 	uint16_t width(void) const { return displayWidth; };
 	uint16_t height(void) const { return displayHeight; };
 
-    // Initialize the display
+    // Prepare the driver for resuming display usage after a deep sleep.
+    // Returns true on success. Returns false on failure (no display detected etc).
+    bool allocateBuffer();
+
+    // Initialize the driver and the display.
+    // Returns true on success. Returns false on failure (no display detected etc).
     bool init();
 
     // Free the memory used by the display